1. Field of the Invention
This invention relates to information retrieval and, more particularly, to an improvement in the manner in which graphic materials are identified in information retrieval systems.
2. Description of the Prior Art
The prior art includes numerous types of apparatus for searching and retrieving graphic material. A survey of several representative types of commercially available automated film retrieval systems appears in Automated Film Systems, Business Automation, September, 1970. The systems described in this survey are designed to retrieve graphic material photographically recorded on either microfiche or strip microfilm supports. In an automated film retrieval system, the film used includes recorded retrieval code patterns that identify segments of the film containing various sections of stored graphic material. Such a system also includes an input terminal from which a user supplies descriptor information that identifies the film segment containing the graphic material to be retrieved and control apparatus that responds to the user-supplied descriptor information and to signals representing the retrieval codes on the film by locating the desired graphic material on the film in a position for viewing or printing.
The prior art discloses numerous techniques for placing retrieval codes on graphic material supports, such as photographic film, which include the use of indicia that can be optically, magnetically, and mechanically detected. Examples of prior art coding techniques and retrieval apparatus are shown in the following U.S. patents: J. F. Cameron et al., U.S. Pat. No. 3,484,751, issued Dec. 16, 1969; P. R. Adams et al., U.S. Pat. No. 3,144,637, issued Aug. 11, 1964; and J. W. Bryce, U.S. Pat. No. 2,124,906, issued July 26, 1938. These prior art coding techniques have two concepts in common: the positions at which retrieval codes are located on a graphic material support, and the placement of code detection apparatus relative to the support for detecting such codes. More specifically, the prior art shows the recording of retrieval codes on a storage surface or a face of the graphic material support with which they are used and these codes are detected by apparatus with sensors that are located adjacent to the support face. While this approach to recording retrieval codes on graphic material supports is useful in many applications, it requires that retrieval codes be stored in portions of the information storage surface of a support, and this reduces the amount of graphic material that can be stored in a particular section of the support. Additionally, there are instances where the operating speed of retrieval apparatus is reduced when it is necessary to locate code detector sensors adjacent to a face of a graphic material support. Also, there are situations where, due to equipment design, it is inconvenient to locate code detector sensors in such a position.